Known process for synthesis of 1,4-thiazine derivative are for example a process starting with a thioglycol amide derivative as disclosed in Journal of the American Chemical Society, 70, 3517 (1948), a process starting with a tricyclic compound as disclosed in Japanese Patent Publication No. 16630/1967 and a process starting with a thiazolium compound as disclosed in Japanese Patent Publication No. 29182/1970.
The fact that pyridone derivatives and pyridazinone derivatives possess properties affecting the cardiovascular systems is described in for example Japanese Patent Provisional Publication No. 48675/1977, Journal of Medicinal Chemistry, 17, 273 (1974) and Japanese Patent Provisional Publication No. 109771/1982.
However, 1,4-thiazine derivatives having nitrogen-containing heterocyclic residue at position 6 are novel compounds and no technique is known for synthesis of such compounds. Furthermore, there is no report on cardiotonic activity of such compounds.